This invention relates to an electrode for secondary battery having high capacity and excellent in charging and discharging characteristics. More specifically, it relates to an electrode for secondary battery which can constitute a cylindrical secondary battery as a flexible and coil-shaped electrode or a sheet-shaped secondary battery as a thin sheet-shaped electrode, particularly an electrode for lithium secondary battery of which the active substance is lithium or an alkali metal composed mainly of lithium.
Electroconductive polymers such as polyacetylene have been proposed as the electrode for secondary lithium batteries.
However, electroconductive polymers cannot be doped with large amounts of lithium ions and also exhibit insufficient polyacetylene.
However, an electroconductive polymer cannot be doped lithium ions with a large amount and is insufficient in electrode capacity and stable charging and discharging characteristics.
Also, an attempt has been made to use lithium metal as the negative electrode of secondary lithium battery, but in this case, the charging the discharging cycle characteristics are not so good. More specifically, during discharging of the battery, lithium moves as lithium ions from the negative electrode body into an electrolyte, while during charging the lithium ions are again electrodeposited as metallic lithium onto the negative electrode. By repeating this charging and discharging cycle, the metallic lithium electrodeposited in these cycles cycle becomes shaped into dendrites. Since the dendrite-shaped lithium is a which results in deterioration of the charging thereby causing an inconvenience to occur that the charging and discharging cycle characteristics of the battery. Further, when this grows until the dendrite-shaped metallic lithium electrodeposited product reaches the positive electrode through the separator, the battery is then short-circuited. That is, the charging and discharging cycle life is short.
To avoid such problems, it has been attempted to use a carbonaceous material of a sintered organic compound as the negative electrode and to carry lithium or an alkali metal composed mainly of lithium thereon.
By this technique, the charging and discharging characteristics of the negative electrode can be dramatically improved, but on the other hand, an electrode molding material which uses this carbonaceous material has poor flexibility, and no satisfactory electrode shaped into a sheet or coil can be obtained.
Also, an electrode in which with use of the carbonaceous material, a large amount of an insulating material such as polyethylene as a binder is used, is excellent in flexibility but electric resistance becomes markedly large so that electrode capacity and output are lowered remarkably.